This application relates generally to the field disc drive storage devices, and more particularly, to an apparatus for reducing transmission of EMI noise originating within a disc drive.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium, such as a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a drive motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator arm (E-block) for movement of the heads relative to the discs. The read/write transducer, e.g. a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment.
Typically, such actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The actuator voice coil motor includes a coil mounted on the side of the actuator arm opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled direct current (DC) is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a bearing assembly mounted on the base plate at a position closely adjacent to the outer extreme of the discs. The head(s) read data and transfer it along the actuator arm to a preamplifier which amplifies the signals coming from the heads.
A flex circuit provides an electrical pathway between the preamplifier of the actuator arm and a disc drive circuit board mounted on an opposite side of the base plate from the actuator and discs. The flex circuit also sends drive signals to the voice coil motor causing the actuator arm to pivot about the bearing assembly thereby changing the position of the head relative to the disc.
Electromagnetic fields induced within the voice coil motor and ground loops within the disc drive create electromagnetic interference (xe2x80x9cEMIxe2x80x9d) noise within the disc drive. Although solutions for reducing the amount transmission within a disc drive of EMI noise originating outside of the disc drive are well known, there is a need to reduce the transmission of EMI noise originating within the disc drive itself. One path for the EMI noise to travel within the disc drive is along the actuator arm (E-block) which corrupts data being transmitted from the read/write head through the preamplifier and to the flex circuit. The corrupted data results in read errors to the disc drive circuit board.
One way to reduce the transmission of EMI noise along the actuator arm and flex circuit is to place conductive tape along the outside of the connection between the base plate and the cover along at least the entire side of the disc drive closest to the actuator assembly. The conductive tape provides an alternative pathway for EMI noise as opposed to traveling along the actuator arm of the disc drive. However, the use of conductive tape is time consuming and costly because the application of tape cannot be accomplished by machinery in the assembly line. Instead, the conductive tape must be manually placed on each disc drive. Additionally, the conductive tape itself is very costly.
It is thus desirable to provide an inexpensive alternative pathway for EMI noise to travel which will reduce the amount of EMI noise traveling along the actuator arm and flex circuit and reduce the amount of read errors in a disc drive. It is further desirable to provide an alternative pathway for EMI noise to travel which can be quickly and easily installed during the manufacturing process of the disc drive.
Against this backdrop the present invention has been developed. The present invention comprises an apparatus and method for reducing the transmission of electromagnetic interference (xe2x80x9cEMIxe2x80x9d) noise originating within a disc drive in order to minimize read errors occurring within the disc drive.
A head disc assembly in a disc drive includes a base plate and a top cover enclosing a drive motor supporting one or more data storage discs thereon and an actuator assembly for transferring data to and from the disc. The actuator assembly includes a flex circuit which provides a path for data transfer between a read/write head and signal processing circuitry external to the head disc assembly.
The amount of EMI noise that reaches a portion of the flex circuit and causes read errors may be reduced by placing an electrically conductive grounding member positioned between a portion of the flex circuit and a source of EMI noise within the head disc assembly. The grounding member has an upper contact portion which electrically contacts the cover and a lower contact portion which electrically contacts the base plate and forms an alternative pathway, as opposed to along the actuator arm, for EMI noise to travel. By providing an alternative pathway, the amount of EMI noise received by at least a portion of the flex circuit is reduced which, in turn, reduces the amount of read errors in the disc drive. Further, the grounding member comprises a part which may be installed by robotic machinery in the disc drive manufacturing process, and may even be incorporated into an existing disc drive subcomponent thereby eliminating the cost of adding an additional part to the disc drive.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.